AFAIK the general practice in all jurisdictions is that each side can challenge a certain number of potential jurors -- some for cause and (I think) fewer without stating a reason. There is a limit, however -- they can't just go on challenging jurors forever! Maybe they had used their limit.
I realize they only have so many objections. But allowing Tim Russert's neighbor?! I'll just have to assume they used all their objections by the time this guy came along.
It could be that they anticipated using their limit. I would have.